The background art teaches several apparatus and methods for perforating or embossing a thermoplastic sheet. For example, U.S. Pat. No. 3,214,795 issued to Hannauer on Nov. 2, 1965 and U.S. Pat. No. 3,243,488 issued to Hannauer on Mar. 29, 1966 teach an apparatus and method to perforate a thermoplastic sheet by passing it between a pattern roll and a heated roll. Hannauer discloses an apparatus wherein the embossing roll and the pressure roll are heated. Complete contact is maintained between the nip of the pressure roll and the embossing roll through use of a rigid pressure roll mounted on a pivot and a piston device which varies pressure applied to the embossing roll by the pressure roll.
U.S. Pat. No. 3,560,601 issued to Johnson on Feb. 2, 1971 teaches a method to emboss and perforate a fabric backed thermoplastic film. Johnson teaches a two step method wherein the material is first embossed by passing between the nip of a studded embossing roll and a pressure roll which embosses but does not perforate the material. In the second step, the material is perforated by blowing hot gases through the weakened film sections created by embossing to create a perforated material.
U.S. Pat. No. 3,707,102 issued to Huppenthal on Dec. 26, 1972 teaches a film perforating apparatus wherein the film is passed over the perforating roll having a series of hot pins which perforate the film. The perforating roll has a generally cool external surface having apertures which contain heated pins. The contact with the heated pins creates the perforations in the film.
U.S. Pat. No. 3,950,480 issued to Adams on Apr. 13, 1976 teaches a method to emboss a plastic film where a sheet of thermoplastic material is indirectly heated as it is passed between two heaters and is subsequently passed between the nip of an embossing roll and a pressure roll. As the heated film is passed between the nip of the embossing roll and pressure roll, it is embossed.
Canadian Pat. No. 664,640 issued to Wangner on June 11, 1963 teaches a method to emboss a vinyl film on a fabric back wherein the vinyl layer of the film is impressed into a heated moving wire belt.
Defensive Publication No. 544,271 published by Zeisberg on Dec. 24, 1968 teaches a method to create an apertured nonwoven structure from a film fibril sheet. Zeisberg teaches the method of passing a film fibril sheet through a nip between an embossing surface having male bosses and a resilient moving surface, at least one of which is heated. The male bosses on the embossing surface are elongated metal wires. Contact of the thermoplastic film with the male bosses in a heated environment causes the thermoplastic fibers to melt and be extruded away from the male bosses to create a film having elongated perforations with grommet-like structures around each perforation. The film material is then stretched thereby causing the elongated slits to become circular.
None of the above disclosed patents teach a method to create an embossed and perforated thermoplastic sheet having embossed cones wherein the perforations are critically located in the apex of each cone of each boss. Furthermore, these references do not teach a method to perforate and emboss a film using a metallic pattern roll rolling against a resilient flexible heating roll.